Gauging the health crisis in Katrina's wake

Emergency health services are finally reaching people with acute health needs in the wake of Hurricane Katrina. And while some experts believe public health risks may have been exaggerated, fears over other risks - such as those posed by contaminated water - are growing.

A futuristic $1.5 million mobile emergency hospital has been set up in a flooded supermarket car park in Mississippi, after red tape prevented doctors from installing the state-of-the-art medical centre in Louisiana - their original destination.

Medical teams in the hospital are treating hurricane survivors based at a nearby "tent city", including hundreds of cases of dehydration and infected wounds. Many of the impoverished survivors have pre-existing chronic health problems such as high blood pressure, diabetes and heart conditions, and had lost their essential medication in the disaster. Pregnant women have been transported to hospitals including several who were in labour.

People have also been turning up with animal bites, says Robert Tosatto, a public health expert and director of the US Medical Reserve Corps. "The floods displaced many wild and domesticated animals and marine life was washed into the area. Doctors have treated lots of bites - some from snakes, some from who knows what animals," he says. "As with all bites from wild animals, there is a risk of rabies," he told New Scientist.

Mosquito-borne infections

But while individuals with acute medical emergencies are finally being tended to, fears are growing about a large-scale public health crisis. Epidemics of cholera, typhoid, malaria and West Nile virus have all been anticipated, and there has already been an outbreak of suspected dysentery in one Mississippi shelter.

While some experts believe the risk for mosquito-borne infections such as malaria and West Nile virus has increased due to the flood waters, others believe the floods may wash the insects' eggs out to sea and that the increasingly salty floodscape will prove unfavourable to them, which may actually lower the risk of these diseases. However, the US Centers for Disease Control and Prevention is starting to carry out mosquito controls in the area and closely monitoring for new outbreaks of West Nile virus.

Disaster health experts say some of the public health risks may have been hyped. They point out that many of the health fears after the Asian tsunami never materialised - there were no epidemics, despite isolated outbreaks of dengue fever, malaria and measles. And, they say, outbreaks of diseases like typhoid and cholera are unlikely in Louisiana because the microbes involved are virtually non-existent in the region.

Cuts and scratches

Fears over the health risks associated with the large numbers of dead bodies in the area are also unfounded, say experts, since, contrary to popular belief, bodies do not pose a risk of infectious disease.

The biggest health risk, medics say, is that posed by contaminated water. Microbes in sewage can cause diarrhoea, hepatitis A and Escherichia coli infections, and people with scratches and cuts risk tetanus - an infection that proved a problem in the aftermath of the tsunami. Pollutants, including toxins from chemical facilities, are exacerbating the generally unsanitary conditions, raising the risk of diarrhoea, respiratory infections and asthma.

"In temperatures upwards of 90°F (30°C), the stress of the situation together with dehydration and injuries relating to the storm itself or the clean-up are causing all kinds of problems, from heart attacks to other emergencies," Tosatto says.

Effects of trauma

Another big risk faced by Katrina's survivors is to their mental health. About 30% of those exposed to severe trauma - defined as being at risk of losing their lives, seeing a person close to them lose their life or seeing dead bodies - are expected to develop an anxiety disorder such as post-traumatic stress disorder.

Among emergency workers involved, including the police, this figure drops to about 5%. "Even those who lose their houses are at a much greater risk of depression and despondency - not psychiatric illnesses, but it can certainly make life much harder for sufferers," says James Thompson, a trauma psychologist at University College London, UK.

"The poorer and older victims who have lost their homes are the most vulnerable, because even if they have lost far less, they know that the probability of their being able to replace their loss is far lower."

But, Thompson says, it is important not to underestimate the resilience of people. Most will have a period of upset and then recover. "Many people actually deal with disaster better than with normal life - studies show that even psychiatric patients behave with absolute lucidity during life-threatening evacuations, only relapsing after danger has passed," he told New Scientist.

"What is crucial now," he says, "is that the organising structure - government, local councils - act fast to ensure that these people are not left miles away in tents with nothing but food and water rations. That will lead to despondency, anger and frustration."

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